CMP head structure with retaining ring

Abstract

A CMP structure for CMP processing and a method of making a device using the same are presented. The apparatus comprises a polishing pad on a platen table; a head assembly for holding a wafer against the polishing pad, wherein the head assembly includes the retaining ring; a sensor for sensing the step height between the retaining ring and its membrane and a controller for adjusting the movement of the retaining ring based on the step height between the retaining ring and its membrane to ensure the step height remains at a fixed value as the retaining ring wears out.

What is claimed is: 
     
       1. A CMP apparatus comprising:
 a polishing pad on a platen table; 
 a head assembly, wherein the head assembly includes a retaining ring for holding a wafer in place on the polishing pad; 
 a ring monitoring equipment configured for sensing and determining a step height between the retaining ring and a membrane of the retaining ring; 
 a controller configured for calculating how much the retaining ring should be moved to ensure the step height between the retaining ring and the membrane remains at a fixed value; and 
 a mechanism configured to move the retaining ring to ensure the step height remains at the fixed value as the retaining ring wears out. 
 
     
     
       2. The apparatus of  claim 1  wherein the step height comprises a first dimension and the controller moves the retaining ring to adjust the step height to ensure it remains at the first dimension throughout the retaining ring life span. 
     
     
       3. The apparatus of  claim 1  wherein the controller activates the mechanism configured to move the retaining ring for adjusting the step height to ensure it remains at the first dimension. 
     
     
       4. The apparatus of  claim 3  wherein the mechanism comprises gears located around the circumference of the retaining ring. 
     
     
       5. The apparatus of  claim 4  wherein the gears are set to be in drive mode at fixed intervals before wafer processing takes place. 
     
     
       6. The apparatus of  claim 1  wherein the retaining ring comprises unfilled polyphenylene sulfide or unfilled polycarbonate which encapsulates a stainless steel ring. 
     
     
       7. The apparatus of  claim 1  wherein the ring monitoring equipment comprises a sensor or a plurality of sensors installed at a head cup load unload (HCLU). 
     
     
       8. The apparatus of  claim 7  wherein the controller receives a measurement of the step height from the HCLU in the form of a digital signal, forwards the digital signal to a control kit that calculates the adjustment needed to keep the step height to a fixed value, receives the calculation of the adjustment needed from the control kit, and activates the mechanism to adjust the retaining ring movement so that it remains at the fixed value. 
     
     
       9. The apparatus of  claim 8  wherein the retaining ring is moved forward to ensure the step height remains at the fixed level and the controller and control kit are merged as one unit. 
     
     
       10. A CMP apparatus comprising:
 a head assembly for use in polishing a wafer, wherein the head assembly includes a retaining ring for holding the wafer in place on a polishing pad; 
 a ring monitoring equipment configured for sensing and determining a step height between the retaining ring and a membrane of the retaining ring; and 
 a controller configured for calculating how much the retaining ring should be moved to ensure the step height between the retaining ring and the membrane remains at a fixed value. 
 
     
     
       11. The apparatus of  claim 10  comprising a mechanism configured to move the retaining ring to ensure the step height remains at the fixed value. 
     
     
       12. The apparatus of  claim 11  wherein the step height is of a first dimension before wafer processing and the retaining ring is moved to ensure the step height remains at the first dimension as the retaining ring wears out. 
     
     
       13. The apparatus of  claim 12  wherein the retaining ring is configured to move forward to ensure the step height remains at the first dimension throughout the retaining ring life span. 
     
     
       14. The apparatus of  claim 10  wherein the controller receives a measurement of the step height in the form of a digital signal, forwards the digital signal to a control kit that calculates the adjustment needed to keep the step height to a fixed value, receives the calculation of the adjustment needed from the control kit, and activates a mechanism to move the retaining ring so that the step height remains at the fixed value throughout the retaining ring life span. 
     
     
       15. The apparatus of  claim 10  wherein the ring monitoring equipment comprises a sensor or a plurality of sensors installed at a head cup load unload (HCLU). 
     
     
       16. The apparatus of  claim 15  wherein the controller receives a measurement of the step height by a step height data controller from the HCLU in the form of a digital signal, forwards the digital signal to a control kit that calculates the adjustment needed to keep the step height to a fixed value, receives the calculation of the adjustment needed from the control kit, and activates the step height data controller to adjust the retaining ring movement. 
     
     
       17. The apparatus of  claim 16  wherein the controller activates a mechanism for adjusting the step height to ensure it remains at the fixed value. 
     
     
       18. The apparatus of  claim 17  wherein the mechanism comprises gears located around the circumference of the retaining ring. 
     
     
       19. The apparatus of  claim 18  wherein the gears are set to be in drive mode at fixed intervals while wafer processing takes place. 
     
     
       20. The apparatus of  claim 10  wherein the retaining ring comprises unfilled polyphenylene sulfide or unfilled polycarbonate which encapsulates a stainless steel ring.